java中的接口interface

接口（interface）是抽象方法和常量值的定义的集合。

从本质上讲，接口是一种特殊的抽象类，这种抽象类值包含方法和常量的定义，没有变量和方法的实现。

TestInterface.java

//唱歌的接口
interface Singer {
	//唱歌
	public void sing();
	//睡觉
	public void sleep();
}

//画画的接口
interface Painter {
	//画画
	public void paint();
	//吃饭
	public void eat();
}

//学生类实现Singer接口
class Student implements Singer {
	//成员变量
	private String name;
	
	//构造方法
	Student(String name) {
		this.name = name;
	}
	
	//get set方法
	public String getName() {
		return name;
	}
	
	public void setName(String name) {
		this.name = name;
	}
	
	//自定义方法——学
	public void study() {
		System.out.println("studying...");
	}
	
	//重写，实现Singer接口里面的方法
	//唱歌
	public void sing() {
		System.out.println("student is singing...");
	}
	//睡觉
	public void sleep() {
		System.out.println("student is sleeping...");
	}
}

//教师类实现Singer，Painter接口
class Teacher implements Singer, Painter {
	//成员变量
	private String name;
	
	//构造方法
	Teacher(String name) {
		this.name = name;
	}
	
	//get set方法
	public String getName() {
		return name;
	}
	
	public void setName(String name) {
		this.name = name;
	}
	
	//自定义方法——教
	public void teache() {
		System.out.println("teaching...");
	}
	
	//重写，实现Singer接口里面的方法
	//唱歌
	public void sing() {
		System.out.println("teacher is singing...");
	}
	
	//睡觉
	public void sleep() {
		System.out.println("teacher is sleeping...");
	}
	
	//重写，实现Painter接口里面的方法
	//画画
	public void paint() {
		System.out.println("teacher is painting...");
	}
	
	//吃饭
	public void eat(){
		System.out.println("teacher is eating...");
	}
	
}

public class TestInterface {
	public static void main(String[] args) {
		//声明Singer接口引用指向Student
		Singer s1 = new Student("le");
		s1.sing();
		s1.sleep();
		//声明Singer接口引用指向Teacher
		Singer s2 = new Teacher("steven");
		s2.sing();
		s2.sleep();
		//将Singer转化为Painter
		Painter p = (Painter)s2;
		p.paint();
		p.eat();
		
		//测试Student和Teacher的自定义方法
		Student s = (Student)s1;
		s.study();
		Teacher t = (Teacher)s2;
		t.teache();
	}
}

结果：

F:\java>javac TestInterface.java

F:\java>java TestInterface
student is singing...
student is sleeping...
teacher is singing...
teacher is sleeping...
teacher is painting...
teacher is eating...
studying...
teaching...

F:\java>

  

 

补充：

Valuable.java

//interface接口
public interface Valuable {
	public double getMoney();
}

//interface接口
interface Protectable {
	public void beProtected();
}

//interface接口继承接口
interface A extends Protectable {
	void m();
	void getMoney();
}

//abstract抽象类
abstract class Animal {
	private String name;
	
	abstract void enjoy();
}

//class类继承abstract，实现interface
class GoldenMonkey extends Animal implements Valuable, Protectable {
	public double getMoney() {
		return 10000;
	}
	
	public void beProtected() {
		System.out.println("live in the room");
	}
	
	public void enjoy() {
		
	}
	
	public void test() {
		Valuable v = new GoldenMonkey();
		v.getMoney();
		Protectable p = (Protectable)v;
		p.beProtected();
	}
}

//class实现interface
class Hen implements A {
	public void m() {}
	public void beProtected() {}
	public double getMoney() {
		return 1.0;
	}
	
	public void getMoney() {}

}